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International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Keeping the yam ‘a part of man’
- a breeder’s contribution
Robert Asiedu
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Benin
Institut National des Recherches Agricoles du Benin (INRAB)
Cameroon
Institute of Agricultural Research for Development (IRAD)
Cote d’Ivoire
Centre National de Recherche Agronomique (CNRA)
Centre Suisse de Recherches Scientifiques en Côte d’Ivoire (CSRS)
University of Abobo Adjame
Ghana
Crops Research Institute (CRI)
Savanna Agric. Research Institute (SARI)
Kwame Nkrumah University of Science and Technology (KNUST)
Nigeria
National Root Crops Research Institute (NRCRI)
University of Ibadan
Ahmadu Bello University, Zaria
Togo
Institut Togolais des Recherches Agronomiques (ITRA)
CIRAD, France
Virginia State University, USA
A breeder
needs many
friends
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Food, Income and Culture
Ethnobotany of yams – Ayensu & Coursey
Interactions of yam and man - Coursey
Sense of identity – Perrot
Yams in society - Degras
Co-speciation of yam and man
Yam festivals
A man’s crop?
Status
The future of yams - Manyong and Nokoe (2003)
Urbanization, Competition, Environmental degradation
Yam and man
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
DomesticationStakeholder analysis:
- 27 villages, Zou Province, Benin
- practised by experienced male yam growers
- in search of more productive varieties (60% of 80 respondents)
- selection based on similarity of leaves to known cultivars (58% of respondents)
Mignouna and Dansi. (2003) Genetic Resources and Crop Evolution 50: 519–528
Scarcelli et al. (2006) Molecular Ecology 15, 2421–2431
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
0
10
20
30
40
50
60
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
Pro
du
cti
on
(m
illi
on
to
ns)
World
Togo
Nigeria
Ghana
Côte d'Ivoire
Benin
Yam
Production
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Yam Area
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
Are
a (
millio
n h
a) World
Togo
Nigeria
Ghana
Côte d'Ivoire
Benin
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Yam Yields in
West Africa
0
2
4
6
8
10
12
14
16
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
Yie
ld (
ton
s/h
a)
World
Togo
Nigeria
Ghana
Côte d'Ivoire
Benin
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Yam supply (g)
per capita per
day 2005
0.00
100.00
200.00
300.00
400.00
500.00
600.00
700.00
800.00
900.00
Togo Nigeria Ghana Côte d'Ivoire Benin
Ya
m s
up
ply
(g
) p
er
ca
pit
a p
er
da
y
Consumption (kcal/cap/day) 2003:
Togo (233), Nigeria (203), Ghana (314), CI (331), Benin (395)
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Key challenges
• Planting materials
• Labour
• Germplasm
• Soil fertility
• Diseases and pests (including weeds)
• Post-harvest handling and processing
Yam Genetic
Improvement
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
High and stable yield of marketable tubers
(per unit of area, labour and time)
Pest and disease resistance
(nematodes, viruses, anthracnose, tuber rots)
Tuber characteristics(size, shape, branching, food quality, storability)
Suitability to cropping systems and tolerance to
abiotic stresses
(shoot morphology, nutrient responsiveness and
use efficiency, tolerance to mid- to late season
drought)
Genetic
Improvement
Objectives
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Dioscorea rotundata
D. alata
D. cayenensis
D. dumetorum D. burkilliana
D. bulbifera D. esculenta
D. opposita D. japonica
D. trifida D. nummularia
D. abyssinica D. praehensilis
Focus on
Selected Food
Yams
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
•Whole tuber
•Tuber fragment
•Milking (double harvest)
•Multiple tuberisation
•Bulbil formation
Planting Materials
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Good performance under no/limited staking
Early maturity and/or multiple tuber production
Suitability to short fallow systems
-Nutrient uptake, responsiveness & use
efficiency
-Pest resistance
Tuber morphology for easy harvesting
Long tuber dormancy
Labour Saving
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Molecular characterization
(genotyping of core collection)
(reference collection)
Ploidy studies using DNA flow cytometry of Dioscorea alata and D. rotundata
AFLP marker diversity of Dioscorea alata
Development of genomic tools for improvement of yam
Characterization
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Characterization
of the core
collection
Figure 1. Genetic diversity tree of 342 yam accessions base
on SSR data using unweighted neighbour- joining analysis
D. alata (red)
D. bulbifera (purple)
D. cayenensis (yellow)
D. dumetorum (ash)
D. esculenta (blue)
D. rotundata (green)
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Creating additional variation:
Interspecific crosses
Parents No. flowers poll. Fruit Set Seed Set
Female Male Number % Number %
D. rotundata D. rotundata 2491 965 38.74 3313 22.16
D. rotundata D. cayenensis 1581 154 9.74 9 0.1
D. rotundata D. alata 1663 6 0.36 9 0.09
D. alata D. alata 8120 1445 17.8 2577 5.28
D. alata D. cayenensis 89 0 0 0 0
D. alata D. rotundata 730 0 0 0 0
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Examination of progenies generated from inter-specific crosses using an isozyme marker confirmed true hybrids
TDr 95/18544 TDc 98-136F1
b
F1TDr 95/19158 TDc 98-136
a
TDr 89/02475 TDc 98-136
+
d
F1
TDr 85/18555 TDc 95-165
F1
C
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D. alata for reaction to yam anthracnose and virus diseases and their effect on yield
Anthracnose and virus diseases of D. alata: effects of yam genotype and planting date
Screening of Dioscorea alata for reactions to viruses
Reaction of Dioscorea rotundata to virus diseases in four agroecological zones
Impact of Yam mosaic virus genus Potyvirus on field performance of white yam
Pathogenic and genetic variability among Colletotrichum gloeosporioides isolates from different yam hosts in the agroecological zones in Nigeria
Evaluation:
Host plant
resistance
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Anthracnose disease
Sources of resistance identified to selected isolates and
used but variability of pathogen is a continuing challenge
Abang et al. 2006. Journal of Phytopathology 154: 51-61
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Sources of resistance identified and hybridized
Odu et al. 2006. Journal of Phytopathology 154: 716-724
Odu et al. 2006. Journal of Phytopathology 154: 688-693
Odu et al. 2004. Field Crops Research 89: 97-105.
Odu et al. 2004. Plant Pathology 53: 141-147
Viruses
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Germplasm
delivery to
partners
Recipient No. of Genotypes
D. rotundata D. alata
2008
AGIP NaOC, Nigeria 24 26
DDS, Nigeria 4 14
PNDRT, Cameroon 21 16
NRCRI, Nigeria 11
2007
CARI, Liberia 57
AARC, Awassa, Ethiopia 30
INRAB, Benin 46 20
ITRA, Togo 16
2006
NRCRI, Nigeria 84 7
INRAB, Benin 12 52
CNRA/CSRS 36 44
CRI, Ghana 17
SARI, Ghana 17
ITRA, Togo 26
Tubercules de TDa 98/01176 préconditionnés
en plein champ pour le stockage dans le
village de Kprakro(Dimbokro) 6 déc.2007
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
National Root Crops Research Institute, Nigeria:
Three new varieties of D. rotundata in 2001
Four new varieties of D. rotundata in 2003
Crops Research Institute, Ghana:
Three new varieties of D. rotundata in 2005
Need for advocacy for yam variety release
protocols
Varietal
releases
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Nematodes
Necrotic spotsCracks & flaking of skin Dry rot
Damage caused by Scutellonema bradys
Galls & crazy rootsGalls
Damage caused by Meloidogyne spp.
Galls and rot
Resistance
identified in
Dioscorea
dumetorum
but not in
the two
dominant
species –
D. alata
and D.
rotundata
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Insect pests of yam tubers
MealybugsScale insects
Tuber moth damageYam beetles
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
The challenge:
Pest build-up
Soil fertility and structure
Vesicular arbuscular mycorrhiza in the nutrition of yams
• Effects of arbuscular mycorrhizal inoculation and phosphorus application on yield and nutrient uptake of yams
• Effect of NPK fertilizer on the tuber yield, leaf nutrient concentrations and mycorrhizal colonization of white yam (Dioscorea rotundata)
Breeding for nutrient responsiveness
Sustainability
(sedentarization) of
yam production
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Colonization (%) of roots of Dioscorea alata by VAM fungi at 4 sites
in Nigeria
Clone Site
Abuja Ibadan Onne Ubiaja Mean
TDa 85/00250 68.00 84.72 39.94 88.32 70.25
TDa 00/00064 78.23 45.09 61.06 88.84 68.31
TDa 00/00104 75.55 55.58 51.98 89.23 68.09
TDa 92-2 72.90 20.91 34.65 75.77 51.06
TDa 99/00395 44.49 45.69 34.78 77.29 50.56
TDa 02/00193 58.97 35.78 48.64 54.64 49.51
TDa 93-36 50.54 28.47 32.48 82.38 48.47
Mean (36 clones) 68.64 45.15 44.31 78.20 59.08
S.e.d: clone = 6.3, location = 2.1, clone x location = 12.6
CV% = 26.1
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Colonization (%) of roots of Dioscorea rotundata at 4 sites in Nigeria
Clone Site
Abuja Ibadan Onne Ubiaja Mean
TDr 97/00588 85.42 78.89 58.38 81.23 75.98
TDr 89/02665 79.38 44.53 78.01 71.50 68.36
TDr 96/01799 79.03 47.67 77.33 69.00 68.26
TDr 96/00528 53.73 49.57 52.90 31.25 46.86
TDr 97/00903 62.38 47.53 1.12 69.78 45.20
TDr 97/00632 56.73 31.45 51.37 40.47 45.01
EHOBIA 33.18 30.53 28.83 44.25 34.20
Mean (for 34 clones) 67.99 43.04 57.11 59.73 56.97
S.e.d: clones = 6.54; Location = 2.24; Clone x location = 13.07
CV (%) = 28.1
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
AM Fungi
0
20
40
60
80
100
120
140
160
180
200
0 0.05 0.5 5
P concentrations (mg P kg-1
soil)
Tu
be
r w
eig
ht (k
g)
mycorrhiza
no mycorrhiza
Tuber yield of TDr 97/00903 as affected by AM
fungal inoculation and P application.
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Tuber yields of
eleven genotypes
of Dioscorea
rotundata at
different
application rates
of NPK 15-15-15
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
01
/00
50
4
93
-31
96
/00
62
9
97
/00
20
5
97
/00
60
9
97
/00
63
2
97
/00
77
7
97
/00
79
3
97
/00
90
3
97
/01
81
8
93
-32
Dioscorea rotundata genotypes
Tuber
yie
ld (
t/ha)
0
200
400
600
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Food and nutritional quality
Description (target attributes for fresh tuber and
flour markets)
Intrinsic and exogenous influences
Effect of tuber harvest time and storage period on
the pasting properties of yam starch
Influence of time of harvest on the yield and
sensory attributes of white yam
Influence of environment and processing on tuber
micronutrient content
Food quality and
end-use suitability
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Screening for tuber contents of total carotenoids, iron, zinc, ascorbic acid, and phytic acid
Variation in retention of total carotenoids, Fe and Zn in Dioscorea cayenensis food products
Influence of environment and genotype x environment interactions on tuber contents of iron and zinc
Total carotenoids (in µg/g fwb)
Dioscorea cayenensis (82 accessions)
Range: 1.25 – 5.12
Mean: 2.72 + 0.80
D. dumetorum
Two accessions with values of 22.29 and 26.60 µg/g
Tuber Density of
Micronutrients
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Tuber content of ascorbic acid (in mg/100g fwb) :
D. rotundata (325 accessions)
Range: 3.56 – 16.87
Mean: 8.3 + 2.26
D. cayenensis (79 accessions)
Range: 4.19 – 11.34
Mean: 7.85 + 1.29
D. dumetorum (31 accessions)
Range: 15.42 – 39.43
Mean: 25.83 + 6.29
Tuber Density of
Micronutrients
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Iron Zinc Ascorbic acid
SOV DF MS % SS MS % SS MS % SS
Total 371 4.90 3.94 2.46
TRT 123 9.74*** 65.8 9.02*** 75.8 4.76*** 64.2
GEN 30 13.76*** 34.4 23.08***62.4 5.68*** 29.2
ENV 3 115.94***29.0 45.60***12.3 61.40*** 31.5
G x E 90 4.86*** 36.5 3.10*** 25.2 2.56*** 39.4
Tuber nutrient contents of 31 genotypes of D. rotundata evaluated
at 4 sites over two years in Nigeria
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Retention (%) of micronutrients in products from
15 genotypes of Dioscorea cayenensis
Boiled yam Pounded yam Flour
Carot. 31-97 9-97 11-75
(69.6) (48.6) (43.2)
Iron 56-99 66-99 18-44
(77.2) (80.3) (29.4)
Zinc 70-96 62-97 13-32
(85.4) (83.6) (22.6)
Micronutrients
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Descriptive statistics for functional (pasting) characteristics of 33 genotypes
of D. rotundata grown at Abuja, Nigeria
Peak
viscosity
Breakdown
viscosity
Final
viscosity
Setback
viscosity
Peak time
(Min.)
Pasting
temp.( C)
Mean 209 38 247 76 6 84
SE 11.7 6.6 12.86 7.66 0.11 0.17
Min. 69 4 97 29 5 82
Max. 338 147 397 209 7 86
Pr. > F ** * * * * * * * ns
* *, *Significant at P<=0.01, and at P=0.05 respectively; ns=not significant
P>=0.05
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
Pea
k Visc.
Troug
h
Breakd
own
Final visc.
Setba
ck
Pas
ting tim
e
Pas
ting temp.
D. alata
D. rotundata
Evaluation of Dioscorea alata varieties for
making pounded yam
Mean pasting
properties of D.
alata and control
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Mean scores for pounded yam from D. alata
Variety Color Smoo. Cons. Elast. Stick. Hard.
Mean 4.66 4.22 3.97 3.56 4.22 4.66
SE 0.27 0.11 0.14 0.14 0.14 0.12
P level *** *** *** ** ** ***
Scale of 1 to 9, where 1= extremely inferior, 2= much inferior, 3= moderately
inferior, 4 = slightly inferior, 5= no difference, 6= slightly better, 7=moderately
better, 8=much better, 9= extremely better
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Keeping yam a
part of man• Is it possible? – yes
• Is it important? – yes!
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
Thank
you
very
much!!